Eszopiclone, also known as (S)-zopiclone or (S)-(6-(5-chloro-2-pyridyl)-5-[(4-methyl-1-piperazinyl)carbonyloxy]-7-oxo-6,7-dihydro-5H-pyrrolo[3,4-b]pyrazine), is formulated as the free base and is sold as LUNESTA®. It is used to treat different types of sleep problems, such as difficulty in falling asleep, difficulty in maintaining sleep during the night, and waking up too early in the morning. Most people with insomnia have more than one of these problems. See, e.g., WO 93/10787; Brun, J. P., Pharm. Biochem. Behav. 29: 831 832 (1988).
The compound eszopiclone and various methods of treatment are disclosed at least in the following U.S. Pat. Nos. 7,125,874; 6,864,257; 6,444,673; 6,319,926; and 5,786,357.
Racemic zopiclone, rac-(6-(5-chloro-2-pyridyl)-5-[(4-methyl-1-piperazinyl)carbonyloxy]-7-oxo-6,7-dihydro-5H-pyrrolo[3,4-b]pyrazine), also formulated as the free base, has been sold in Europe for many years to treat different types of sleep problems.